Oil from hydroxylated fatty acids



Patented Sept. 16, 1941 Scott Long, Coopersburg, Pa., assignors to Devoe& Raynolds Co., Inc., a corporation of New York No Drawing. ApplicationMarch 12, 1938, Serial No. 195,550

Claims.

Usual natural oils are glycerides of higher unsaturated fatty acids. Inrecent years, considerable study has been given to the preparation ofsynthetic oils and related compounds f the alkyd resin type and in suchcase the synthetic bodies produced ordinarily are glycerides or estersof comparatively low molecular weight polyhydric alcohols. At varioustimes (as 'in times of war or threatened war) there are many demands forglycerine and its usual equivalents, and at the same time fatty acidsare relatively plentiful. The present invention relates to themanufacture of oils from natural fatty acids without the use ofglycerine or what are normally considered equivalent types of alcohol.

This invention is based on our discovery that if the fatty acids ofdrying oils are hydroxylated, they can readily be converted intosubstantially neutral oils in various manners. Thus if the hydroxylatedacids are heated, they will undergo inter or intra esterification toform lactones or lactides or other substantially neutral molecules, orsuch hydroxylated acids can be esterified with other acid bodies whichmay themselves be fatty acids of drying oils or may be lower fattyacids, or which may be other acid bodies of a film-forming nature suchas the acids of natural resins, or various carboxylic acids such asphthalic acid or maleic acid or the like. Since the hydroxylated dryingoil acids will have both active hydroxyl groups and also carboxylgroups, the reaction may be somewhat controlled by first blocking thecarboxyl groups. This can be accomplished by esterifying thehydroxylated fatty acids with a simple monohydric alcohol, and for thispurpose we have found methyl alcohol particularly efiicient, as theesterification can be conducted under conditions which will not causesubstantial inter or intra esterification of the hydroxylated molecules,thus leaving the hydroxyl groups available for further reaction.

The degree of hydroxylation of the fatty acids will of course bear somerelation to the degree of unsaturation of the oil treated, for of courseoleic acid will develop fewer hydroxyl groups than a more unsaturatedacid such as the drying oil acids. However the proportionate yield ofhydroxylated acids tends to decrease as the iodine number of the acid tobe treated increases, due to the development of oxidized by-products andproducts of degradation.

The hydroxylation may be accomplished by the use of various oxidizingagents such as potassium permanganate or hydrogen peroxide. The

addition of hydroxyl groups tov the various oil fatty acids gives riseto the formation of a number of isomers similar to those found in sugarchemistry. Generally speaking, we have found that the hydroxylated fattyacids prepared by the use of hydrogen peroxide have a lower meltingpoint than those prepared by the permanganate method. This observationapplied particularly to the treatment of mixed acids suchas thoseobtained from natural oils. In the examples given hereafter thehydroxylation is carried out by the permanganate method except where theperoxide method is particularly indicated.

In our use of the hydrogen peroxide method, the unsaturated fatty acidsto be hydroxylated were dissolved in glacial acetic acid to which aquantity of 30% hydrogen peroxide solution was added. The mixture wasplaced on awater bath and gently heated. After a few minutes the fattyacid layer disappeared and the whole solution became homogeneous. Thesolution bubbled, indicating the progress of the reaction. The majorportion of the reaction took place in about 30 minutes as indicated bythe frothing, but heating was continued for a total of at least 4 hours.

When treating oleic acid having an iodine number of about 89,satisfactory results were had when 280 parts of this acid were used with800 partsof the glacial acetic acid and 292 parts of 30% peroxide.

With sunflower oil acids having an iodine number of between 135 and 145,210 parts were employed, with the same amounts of acetic acid andperoxide as given above; in the case of linseed fatty acids having aniodine number of between" 170 and 180, only 140 parts of the oil acidswere used. 7

After the heating has been completed, the

acetic acid solution was cooled and the hydroxylated acidscrystallizedout. They can be filtered off and freed of acetic acid bywashing successively with water and petroleum ether. Acetic acid may berecovered by adding additional water to precipitate further acids andthen distilling off the acetic acid, leaving a viscous residue insolublein petroleum ether which gives tests for the presence of peroxide oxygenand the carbony. group. v

The use of permanganate is illustrated by the following procedure:

For 168 grams of oleic acid of an iodine number of 89, 50 grams ofpotassium hydroxide in one liter of water were first used to saponifythe acids. The solution of 168 grams of potassium permanganate in 6liters of waterwas gradually added for a period of 2 to 3 hours to thepotasalum oleate which was kept very cold and rapidly stirred during thereaction. Stirring was continued for one hour after the final additionof the permanganate solution. The mixture became mushy and attained abrown to black appear;- ance. Sulphur dioxide was now passed into thismixture until it became white, thus liberating the hydroxylated acids.If desired, a small amount of hydrochloric acid may also be added atthis point. The white hydroxylated acids are filtered, washed thoroughlywith water and refiuxed with textile spirits (aliphatic hydrocarbonswith a boiling point of 65 to 100 C.) and filtered. The process isrepeated twice. This removes stearic acid or unhydroxylated acids. Thefollowing table indicates proportions oi reagents which we have employedwith various types of oils:

The hydroxylated acids prepared in this manner are saturated, that is,they contain substantially no ethenoid linkages.

Since these hydroxylated acids contain both carboxyl and hydroxylgroups. they can be subiected to both inter and intra esterification toform lactones and lactides by simple heating, but we have found thatthis reaction is best conducted in the presence of a solvent such forexample as an aliphatic hydrocarbon type of solvent with a boiling rangein the order of about 200 0.

Itistobeunderstoodthatourreferencetothe formation of lactones andlactides is intended only to give an indication of the type of reactionthat may go on and that other types of large molecules may be produced,but these are all substantially uniform as regards acidity and hydroxylcontent, as after the reaction caused by heating, an unesterifiedhydroxyl group remains intact for each acid residue. As an alternativethe hydroxylated acids may be subjected directly in esterification withotheraclds or they may first be given a self-esterification treatmentand subsequently acidified with additional fatty acids. In such case ifa solvent has been employed, it may be removed by distillation beforethe addition of further unhydroxylated fatty acids.

As illustrated by the examples which will be given hereafter, acidsemployed may either be other oil acids or simpler fatty acids such asacetic acid may be used, or we may employ other types of acid such asrosin acids or the resinforming carboxylic acids such as phthalic acidand maleic acid and the like.

If esterification of the hydroxylated acids and other acids is to beaccomplished with the aid ofheat (asisusuallythecase) interandintraesterification will tend to go on simultaneously.Ifthisisnotdesired,itcanbeavoidedbyfirst blocking oil. the reactivecarboxyl groups of the hydroxylated acids. Since self-esterification isto be avoided, this blocking oif cannot be carried out by the usualesterification methods involving heat. However, we have found that thisblocking methyl alcohol following the following proceure:

About parts of the hydroxylated acids were dissolved in 150 parts ofmethanol and made alkaline to phenolphthalein by the cautious additionof a 50% aqueous solution of potassium hydroxide. To the resultingalcoholic soap solution, an equal mol portion (the amount depending onthe molecular weight of the acids) of dimethyl sulphate was added. Afterstanding for 24 hours at room temperatures crystals of potassium methylsulphate separated. Water was then added which precipitated the methylester of the oil can be eiilciently accomplished by the use of hydroxyacids and disolved the crystals; The ester was filtered 01! and washedwith several portions of a 1 to 2% sodium carbonate solution followed byseveral washings with hot water.Theesterwasthendriedbyheatinguntilitbecame a liquid and water was nolonger evolved.

The resulting methyl esters of hydroxylated acids are white and wax-likepossessing melting points ranging-from 04' to 6., which is hi her thanthe melting points of most commercial waxes. These products are not verysoluble in organic solvents as single components but they havesuiiicient solubility so that they not only are available asintermediate products for the processes herein set forth, but they mayalso be employed in a mixture of solvents as lubricants for lacquers.These methyl esters of hydroxylated acids having free hydroxyl groupscan be usedforesterifyingothertypesof acidsasalready referred to. Wehave found that the best results were accomplished at temperatures vofbetween 230 and 240 (busing carbon dioxide to maintain agitation andremove water of reaction. Generally speaking, the secondary alcoholgroups which are found in these hydroxy-' lated acids require a highertemperature for esterification than do the simple alcohols.

During the esterification process the free hydroxyl gr ups that areuncombined are reduced toasmall fraction of theiroriglnal valueandthefinalacidvalue ishigh. However,ithasbeen found that the reaction masstends to come to an equilibrium showing a definite acidity. Itmaybethatthisistheresultofthecompounds undergoing some slightdehydration within themselvesso'thatthefinalalcoholintheoii possesses anethenoid linkage, whereas, the 11 1. mi alcohol was saturated. In anyevent, when such acidity is found, it may be advisable to addsufiicientalcoholtoreduceoreliminatethis acidity and thereby increasethe complexity of the eompoimd. For this purpose, glycerol has been:found particularly advantageous, but other alcohols, particularly polyydric alcohols, may be employed.

In the examples which follow, after the various types of drying oilesters were prepared, each was compared with an alkaline refined linseedoil in order to judge of the properties of the new product. The driersused in each case (except where otherwise specified) were: .3% Pb, .02%Mn and .02% Co. The film thicknesses were .02 of an inch. The oils weredried under standard conditions of light, 70 1". and 50% relativehumidity. The drying time of the standard linseed oil was about .5hours. In niost cases, the prepared oilsdriedintimeshorterthan5hoursandhada water resistance equal to or betterthan the natural oil. In all cases, the esters containing China-woodfatty acids were by far the superior.

This evidence then points specifically to the very definite influence ofthe type of acid radical, rather than the alcohol, on water resistance.

Example N0. 1.Sunflower oil fatty acids were hydroxylated by thepermanganate process. The hydroxylated acid averages 3 hydroxyl groupsper mol and had an iodine absorption of 6%. Of the hydroxylatedsunflower acids, 17 parts were heated with 29 parts of linseed oil acidsto 'a temperature of between 220 C. and 230 C. for 12 hours, and gentlyagitated with a stream of CO2 gas. At the end of that time the acidvalue remained constant at 63.5 mg. KOH/g. The product was then washedseveral times with methanol to remove the greater portion of the freeacid.

The finished product had the following constants:

Acid number 25 mg. KOH/g. Saponification value. 186 mg. KOH/g. Acetylvalue 21 mg. KOH/g. original oil.

This oil dried to a smooth film with driers in about 3 hours. Its waterresistance was about the same as linseed oil.

Example No. 2.Linseed oil fatty acids were hydroxylated in accordancewith the permanganate method giving rather poor yields. Due todecomposition, the resultant acids averaged 2 hydroxyl groups permolecule and had an iodine absorption of 3%. 25 parts of thesehydroxylated acids were heated with 22 parts of additional linseed oilacids for 12 hours at a temperature of from 220 to 230 C. while beinggently agitated with CO2 gas. The acidvalue remained constant at 62 mg.KOH/g. After washing with methanol, the ester had the followingconstants:

Acid value 26 mg. KOH/g. Saponification value 195.5 mg. KOH/g. Acetylvalue -1 Nil.

This oil dried to a smooth film in about 6 hours with driers. Its waterresistance was about the same as that of linseed oil.

Example N0. 3.This example was exactly similar to Example No. 2, exceptthat Chinawood oil acids were combined with the hydroxylated linseed oilacids. The methanol washed product had the following constants:

Acid value 34 mg. KOH/g. Saponification value. 187 mg. KOH/g. Acetylvalue mg. KOH/ g. original oil.

This product was very viscous and dried to a smooth film with driers inabout 3 hours. Its water resistance was considerably better than that oflinseed oil.

Example No. 4.In this example the hydroxylated acids were produced fromsafflower oil and averaged 3.7 hydroxyl groups per molecule with aniodine absorption of 6%. 25 parts of these hydroxylated acids were mixedwith 27 parts of linseed oil fatty acids and 27 partsof China-wood oilfatty acids in 100 parts of hy- Acid value 33 mg. KOH/g. Saponificationvalue- 186.5 mg. KOH/g. Acetyl value 22 mg.KOH/g.origmalo1l.

This 011 dried to a smoothfllm with driers. Its water resistance wasbetter than that of linseed oil. p .4

Example No. 5.In this example hydroxylated safflower acids were refluxedwith methanol. In such case the highly hydroxylated acids remainedinsoluble and can be filtered from the alcoholic solution containinglargely the dihydroxy acids. The particular fraction of hydroxylatedacids used in this example average 2.5 hydroxyl groups per molecule. Theiodine absorption was 6%. 20 parts of these hydroxylated acids werecombined with 25.4 parts of China-wood oil acids using 60 parts ofsolvent as in Example No. 4. The recovered viscous oil had the followingconstants:

Acid value 27.5 mg. KOH/g. Saponification value 188.5 mg. KOH/g.

It dried to a smooth tough fllmin 2 hours. Its water resistance wasconsiderablybetter than that of linseed oil.

Example No. 6.-Hydroxylated castor oil fatty acids were esterifled withmethyl alcohol as described above. The resulting product averaged 3.4hydroxyl groups per molecule with an iodine absorption of 9%. 20 partsof these hydroxylated acids were heated with 54 parts of linseed acidsfor 15 hours at a temperature of from 230 to 240 C.- while agitation wascontinued with a stream of C02. At the end of that time the acid valueremained constant. The product was washed several times with methanoland had the following constants:

Acid value 18 mg. KOH/g. Saponification value 197 mg. KOH/g. Acetylvalue Nil.

This product dried to a smooth film in 4 hours and showed waterresistance equivalent to that of linseed oil.

Example No. 7 .-The methyl esters of hydroxylated sunflower acids wereproduced averaging 3 hydroxyl groups per molecule with an iodineabsorption of 6%. 20 parts of these acids were heated with 49 parts oflinseed acidsfor 15 hours as in Example No. 6. The product had thefollowing constants:

Acid value 23 mg. KOH/g. Saponification value 195 mg. KOH/g. Acetylvalue Nil.

This oil dried to a smooth film with driers in about 5 hours. Its waterresistance was about the same as linseed oil. r

Example No. 8.54 parts of hydroxylated sunflower acids averaging 3hydroxyl groups per molecule with an iodine absorption of 6% were mixedwith parts ofhydrocarbon solvent having a boiling point of from 192 to207 C. This mixture was refluxed and the distillate received in aBidwell 8: Stirling tube so that the solvent returned tothe mixturewhile the water was captured, such refluxing continuing for 8 hoursuntil the mixture was practically neutral. The solvent was removed bydistilation and vacuum. The resultant product was very viscous andplastic and possessed the following constants:

Acid value 2.7 mg. KOH/g. Saponification value- 149 mg. KOH/g.

Acetyl value 49 mg. KOH/g. original oil. Iodine value 3.4%.

' stants: Acid value .jNil,

Saponiflcation value 164 mg. KOH/g.

This product dried. to a soft plastic film with driers.

Example N 5 parts of hydroxylated lin- ,see'l acids as in Example No. 2were heatedwith 22 parts of ordinary linseed acids for 12 hour'sat atemperature of 220 to 230 C. while being gently agitated with CO: untilthe acid value remained substantially constant at 88 mg. KOH/g. 38.8parts of this product was then mixed with 1.8

parts of glycerol and the mixture was heated for 8 hours at atemperature or 220 to 230' C. until the acid value reached 12.2 mg.KOH/g. This product had a saponification value of 188 mg. KOH/g. and anacetyl value of 25.5 mg. KOH/g. of original oil.

The oil dried to a smooth film in 3% hours with drier. Its waterresistance was about the same as that of linseed oil.

Example No. 11.--An ester, methyl dihydroxy stearate (containing 2hydroxyl groups per molecule) was prepared. 14 parts of this stearatewere heated with 22 parts of rosin (W. G.) at 240 C. for 10 hours whenthe acid value remained constant at 76 mg. KOH/g. The resultant productresembled ester gum in physical properties.

Example No. 12.200 parts of saiiiower oil were mixed with 250 parts of30% peroxide solution and 400 parts of glacial acetic acid. The mixturewas refluxed on a water bath for 4 hours. As

. soon as the reaction mixture became warm the reaction became quitevigorous. This required about 45 minutes and continued for about 30minutes. The heating was continued for between 2% and 3 hours after thisvigorous action ended.

Water was then added and the product washed free of acetic acid anddried over anhydrous sodium sulphate. The oxidized product had anacetylation value of 165 mg. KOH/g. parts of this oil were esterifiedwith 41 parts of linseed oil fatty acids for 8 hours, at a temperatureof 200 C. by passing carbon dioxide through the agitated reactionmixture. At the end of this time heating was discontinued because themixture was becoming very viscous. The acid value at this point was 18.8mg. KOH/g whereas, the value of the original mixture was 81.4 mg. KOH/g.

The final product was very viscous and was diluted with an equal volumeof toluene. When treated with .02% cobalt as a drier it dried to asmooth, tough fllm in 2% to 3 hours.

E:rample No. 13.The white methyl ester of mixed hydroxylated oleic.simfiower, saillower and linseed oil acids was refluxed for 2 hours withabout twice its weight of acetic anhydride. A small quantity ofanhydrous sodium acetate (about 6% of the weight of the anhydride) wasadded. The reaction mixture was poured into "water and washed until theaqueous washings were neutral to litmus. This took four washings in hotwater. The oily acetates of a yellowish brown color were then dried overanhydrous sodium sulphate.

These acetates were used as a plasticizer in nitrocellulose according tothe following formulation:

The resulting lacquer was diluted to praying consistency and sprayed onaluminum and copper panels, in comparison with a similar lacquer made upwith dibutyl phthalate as a plasticiaer. The properties of the lacquerfilms as regards adhesion and hardness were practically identical.However, it was found that the plasticixing action of these novel estersper unit weight was greater than that of dibutyl phthalate and for thatreason smaller quantities could be used to advantage.

It is understood that the foregoing examples are given only by way ofillustration and may be modified in many particulars without departingfrom the spirit of our invention.

What we claim is:

1. A synthetic drying oil consisting of the reaction products of ahydroxylated compound of a drying oil acid having at least two hydronlgroups esterified with at least two molecules of drying oil acid foreach molecule of such hydroxylatedcompound. such product beingcharacterized by the fact that it has a number of double bonds permolecule at least approximately equal to the aggregate number of doublebonds in said last specified drying oil acid molecules.

2.Anoilasspecifiedinclaim1inwhichthe hydroxylated compound of the dryingoil acid is esterified in the carboxyl end with a monohydric alcoholradical.

3. A method of producing a synthetic drying oil which comprisespreparing the hydroxylated compound of a drying oil acid having at leasttwo hydroxyl groups and esterifying such hydroxylated compound with atleast two molecules of drying oil acid for each molecule of suchhydroxylated compound while maintaining the double bonds of said lastspecified drying oil acid molecules substantially unsaturated.

4. A method as specified in claim 3 which includes the further step ofneutralizing by esterifying at the carboxyl end with an alcohol.

5. The method of preparing synthetic drying oils which comprisesreacting with unsaturated drying oil acids a hydroxylated compoundrepresented by the formula CI'I2CnH2a-c(OH) :COOR, inwhichnis at least16 andzatleast2andRis a member selected from the group consisting ofhydrogen and the CH: radical, to produce a compound having a degree ofunsaturation approxi mately corresponding with the number of doublebonds of the drying oil acids.

ALFRED E. RHEmECK. JAMES SCOTI LONG.

